Distribution of Pleural Injectate

Effect of Volume of Injectate and Animal Rotation

¹ From the Instituto do Coracao of the Faculty of Medicine of the University of Sao Paulo, Brazil, and the Department of Medicine of the Veterans Administration Medical Center, Long Beach, Calif, and the University of California Irvine

It is controversial whether rotation is necessary for patients undergoing pleurodesis. In addition, the optimal volume of the injectate remains to be determined. The purpose of this study was to determine the importance of rotation and the volume of the agent on the intrapleural dispersion of agents injected into the pleural space of rabbits. Technetium 99m pertechnetate (^99mTc) in 0.5, 1.0, or 2.0 ml of saline solution was injected into ten lightly anesthetized rabbits, half of whom were rotated for 1 min after the injection. Static images were obtained in the anterior projection 1 and 5 min after the injection. After the second scan, the limits of the lung were defined by obtaining a perfusion scan immediately after the intravenous injection of macroaggregates of ^99mTc-labeled serum albumin. The degree of dispersion was significantly greater in the nonrotated groups both at 1 min (F=8.11, p=0.0085) and at 5 min (F=5.89, p=0.0274). In addition, the homogeneity of the distribution of the injectate was not improved with rotation. From this study, we conclude that rotation of the animal for 1 min after the intrapleural injection does not improve the distribution of the injectate throughout the pleural space. Furthermore, a volume of 0.5 ml is sufficient for all pleural surfaces to be exposed.

Key Words: pleural effusion • pleurodesis • pneumothorax